Radiocarbon Date List X: Baffin Bay, Baffin Island, Iceland, Labrador Sea, and the Northern North Atlantic

Date List X contains an annotated listing of 213 radiocarbon dates determined on samples from marine and terrestrial environments. The marine samples were collected from the East Greenland, Iceland, Spitzbergen, and Norwegian margins, Baffin Bay, and Labrador Sea. The terrestrial samples were collected from Vestfirdir, Iceland and Baffin Island. The samples were submitted by INSTAAR and researchers affiliated with INSTAAR\u27s Micropaleontology Laboratory under the direction of Dr.’s John T. Andrews and Anne E. Jennings. All of the dates from marine sediment cores were determined from either shells or foraminifera (both benthic and planktic). All dates were obtained by the Accelerator Mass Spectrometry (AMS) method. Regions of concentrated marine research include: Baffin Bay, Baffin Island, Labrador Sea, East Greenland fjords, shelf and slope, Denmark Strait, the southwestern and northwestern Iceland shelves, and Vestfirdir, Iceland. The non-marine radiocarbon dates are from peat, wood, plant microfossils, and mollusc. The radiocarbon dates have been used to address a variety of research objectives such as: 1. determining the timing of northern hemisphere high latitude environmental changes including glacier advance and retreat, and 2. assessing the accuracy of a fluctuating reservoir correction. Thus, most of the dates constrain the timing, rate, and interaction of late Quaternary paleoenvironmental fluctuations in sea level, glacier extent, sediment input, and changes in ocean circulation patterns. Where significant, stratigraphic and sample contexts are presented for each core to document the basis for interpretations

Mass extinctions drove increased global faunal cosmopolitanism on the supercontinent Pangaea

Mass extinctions have profoundly impacted the evolution of life through not only reducing taxonomic diversity but also reshaping ecosystems and biogeographic patterns. In particular, they are considered to have driven increased biogeographic cosmopolitanism, but quantitative tests of this hypothesis are rare and have not explicitly incorporated information on evolutionary relationships. Here we quantify faunal cosmopolitanism using a phylogenetic network approach for 891 terrestrial vertebrate species spanning the late Permian through Early Jurassic. This key interval witnessed the Permian–Triassic and Triassic–Jurassic mass extinctions, the onset of fragmentation of the supercontinent Pangaea, and the origins of dinosaurs and many modern vertebrate groups. Our results recover significant increases in global faunal cosmopolitanism following both mass extinctions, driven mainly by new, widespread taxa, leading to homogenous ‘disaster faunas’. Cosmopolitanism subsequently declines in post-recovery communities. These shared patterns in both biotic crises suggest that mass extinctions have predictable influences on animal distribution and may shed light on biodiversity loss in extant ecosystems

Holocene Cyclic Records of Ice-Rafted Debris and Sea Ice Variations on the East Greenland and Northwest Iceland Margins

The dynamics of the Greenland Ice Sheet and drift of sea ice from the Arctic Ocean reaching Denmark Strait are poorly constrained. We present data on the provenance of Fe oxide detrital grains from two cores in the Denmark Strait area and compare the Fe grain source data with other environmental proxies in order to document the variations and potential periodicities in ice-rafted debris delivery during the Holocene. Based on their Fe grain geochemistry, the sediments can be traced to East Greenland sources and to more distal sites around the Arctic Basin. On the Holocene time scales of the two cores, sea ice biomarker (IP25) data, and quartz weight percent reveal positive associations with T°C and inverse associations with biogenic carbonate wt%. Trends in the data were obtained from Singular Spectrum Analysis (SSA), and residuals were tested for cyclicity. Trends on the environmental proxies explained between 15 and 90% of the variance. At both sites the primary Fe grain sources were from Greenland, but significant contributions were also noted from Banks Island and Svalbard. There is a prominent cyclicity of 800 yrs as well as other less prominent cycles for both Greenland and arctic sources. The Fe grain sources from Greenland and the circum-Arctic Ocean are in synchronization, suggesting that the forcings for these cycles are regional and not local ice sheet instabilities

A constitutive material modelling methodology for asphalt mixtures

Trabajo de investigaciónObjetivo general: Identificar las características clínicas y epidemiológicas de las urgencias oftálmicas en el Centro Médico Naval Cirujano Mayor Santiago Távara 2019. A nivel mundial, se estima que aproximadamente entre 30 y 40 millones de pacientes con ceguera han evidenciado lesiones traumáticas y no traumáticas, en la mayoría de casos evitables. Se ha reportado un valor de 52% para ceguera monocular y 20% para ceguera bilateral, frecuentemente ocasionadas por contusiones mecánicas. América Latina y El Caribe evidencian una situación similar, ya que, según la Organización Panamericana de la Salud, por cada millón de habitantes, se hallan 5000 pacientes con ceguera y 20 000 con algún grado de discapacidad visual, cuyos orígenes, en el 80% de los casos, son prevenibles. En el Perú, se evidencia una realidad antitética, ya que, según el Instituto Nacional de Oftalmología Dr. Francisco Contreras Campos, la población nacional reporta una mayor preponderancia entre las edades de 5 y 19 años (33%), con mayor afluencia en la población masculina (10 509 atenciones), a consecuencia de traumatismos por cuerpos extraños en la córnea (3041 casos) y con la facoemulsificación más lente intraocular como procedimiento quirúrgico ejecutado con mayor asiduidad (2554 casos/ permanencia 1.8 días). Finalmente, contextualizando esta realidad en el Centro Médico Naval Cirujano Mayor Santiago Távara, se constata que, a pesar de contar con modernos equipos de microcirugía oftálmica y con un cuerpo médico especializado en el manejo de patologías de retina y humor vitreo, no se halla una tasación estadística que permita conocer la realidad de la institución; es así, que se torna imprescindible ejecutar una investigación que posibilite la determinación de la frecuencia y cada una de las características clínicas y epidemiológicas de las urgencias oftálmicas, con la única finalidad de dilucidar su verdadero comportamiento y adoptar medidas preventivo-promocionales, en beneficio del paciente y el profesional